Fracto-emission in lanthanum-based metallic glass microwires under quasi-static tensile loading

Abstract

Plastic deformation in metallic glasses is highly localized and often associated with shear banding, which may cause momentary release of heat upon fracture. Here, we report an explosive fracture phenomenon associated with momentary (∼10 ms) light emission (flash) in Lanthanum-based (LaAlNi) metallic glass microwires (dia. ∼50 μm) under quasi-static tensile loading. The load-displacement data as well as the visual information of the tensile deformation process were acquired through an in situ measurement set-up, which clearly showed nonlinear stress (σ)–strain (ϵ) curves prior to yielding and also captured the occurrence of the flash at high fracture stresses (∼1 GPa). Through the postmortem fractographic analysis, it can be revealed that the fracto-emission upon quasi-static loading could be mainly attributed to the localized adiabatic work accumulated at a very large elastic strain confined within the microscale sample volume, followed by a localized high temperature rise up to ∼1000 K at the fracture surface through localized energy dissipation. Our findings suggest that the La-based metallic glass microwires could be useful for energetic microchips, micro-ignition devices, and other functional applications.